Modern turbofan engines usually comprise a fan rotor and one or more core rotors. Generally, in operation, the rotor blades in the fan rotor rotate about the shaft to compress a flow of air. The resulting supply of compressed air is then supplied to the core rotors when further compression occurs and then to the combustor where energy in the form of combusted fuel is added to the flow stream. The resulting flow of hot gases from the combustor is expanded through several sets of turbines, which causes the turbine rotor blades to rotate about the shaft. In this manner, the energy contained in the fuel is converted into the mechanical energy of the rotating blades, which may be used to rotate the rotor blades of the fan and/or the coils of a generator to generate electricity.
The ever-increasing demand for energy makes the objective of engineering more efficient turbofan engines an ongoing and significant one. Specifically, it's desired to improve the turbofan engine's overall pressure ratio (OPR) for better efficiency. Furthermore, it is also desired to reduce the booster stage count to get a more compact turbofan engine.